There are a few different careers available that might allow you to play video games for money. Becoming a game tester is probably the most well-known option and also generally the easiest. These people spend their days playing games that are still in development, searching for problems and providing feedback to the designers. If you have a very high skill level in the right kinds of games, you might also be able to play video games for money as a professional gamer by joining a team or competing in tournaments.
When a team of designers and technicians are working on a game, they often lose perspective on the quality of their work. It can be very useful for them to get feedback from other people who haven't spent hours and hours running through the same section repeatedly. This is one of the main reasons that companies generally hire game testers.
Another major job for game testers is to look for bugs in the game code. Some games are very large, and in the early stages of development, there can be many little problems that the designers haven't discovered. Sometimes these problems will only show up on certain hardware or under very unusual circumstances. Game testers are often asked to play through sections of the game under a wide variety of circumstances to find exactly what is causing various bugs.
If you choose to be a game tester, finding a job where you play video games for money might not be all that hard. The requirements are generally relatively lax compared to many other game industry jobs. You'll need to be a skilled gamer, and you need to know a lot about video games, including having a good understanding of the process involved in creating them. You will also probably need a fair amount of patience because playing games before they are finished isn't necessarily always fun. One thing you might want to consider is moving to an area where there are a large number of game companies hiring.
Certain gaming genres have become popular enough that people have basically turned them into sports. Most of these are multi-player games, and generally, they are designed primarily for online play. If you want to play video games for money as a competitive gamer, you will need to be highly skilled. The competition is very intense, and experts suggest that it requires the same kind of extreme dedication as any professional athletic endeavor. You may also have to work your way up for a long time if you want to get to the point where you make most of your money through competitive gaming, and you may have to master brand new games from time to time in order to keep up with the most popular trends.